Pattern electroretinogram (PERG) in the early diagnosis of optic nerve dysfunction in the course of Graves’ orbitopathy

Introduction
The present study was design to evaluate the pattern electroretinogram in the diagnosis of early changes in visual function of patients with Graves’ orbitopathy without perimetrical signs of optic nerve neuropathy.

Material and methods
19 eyes from ten patients, mean age 36 ± 6.8 SD, comprising (7 F and 3 M) with GO, affected by (1–4) NOSPECS severity class were enrolled in the study. 22 eyes from eleven healthy volunteers served as a control. The pattern electroretinogram was recorded with TE-1000 headset electrode using PRIMUS 2,5 (Tomey). The temporal frequency of PERG was 2 Hz and the check size was 1°. Student’s t-test was used for the statistical analysis of mean and standard deviations. Statistical significance was assumed at p < 0.05 for all analyses. Cut-off points, sensitivity and specificity of the pattern elektroretinogram parameters assessed by receiver operating characteristic curves were performed by Medcalc ®.

Results
In patients with Graves’ orbitopathy a significantly decreased P50 amplitude was found (2.04 ± 0.99 vs. 2.69 ± 0.88 in healthy controls). Receiver operating characteristic curves analysis revealed a high sensitivity of P50 amplitude and N95- P50 amplitude for discrimination between Graves’ orbitopathy and healthy group (78.9% and 81.8%, respectively). The specificity of P50 amplitude was fairly high (63.6%) while N95-P50 amplitude was rather low (47.4%).

Conclusions
The reduction of the P50 amplitude could be a marker of an early ischemic optic nerve dysfunction in patients with Graves’ orbitopathy. The evaluation of the pattern electroretinogram P50 and N95-P50 amplitude might be a fairly sensitive test for screening dysthyroid optic neuropathy.